Mutagenicity testing of seminal fluid: seminal fluid increases the mutagenicity of the precursor mutagen benzo[a]pyrene in the presence of S9 mix

Small amounts of seminal fluid strongly enhanced the mutagenicity of the precursor mutagen benzoa]pyrene (BP) in the Salmonella/microsome test. This previously unreported effect was found only in the presence of S9 mix for metabolic activation. The increase far exceeded the additive effect expected from experiments where seminal fluid and BP were tested separately with S9 mix. Testing of the direct-acting mutagen 4-nitro-o-phenylene-diamine (NPD) together with seminal fluid resulted in a lower mutagenic activity than that of NPD alone. Seminal fluid had a bactericidal effect on the Salmonella bacteria, thus only volumes up to 40 microliter could be used per plate. The mutagenic effect of only seminal fluid and S9 mix was slightly increased over controls in a standard Ames test, but was equal to the spontaneous mutation rate with a preincubation test modified according to Kado and coworkers. There were no significant differences between seminal plasma from smokers and non-smokers in any experimental series. Seminal fluid concentrated 20-fold by extraction with the mutagen-removing adsorbant Mutasorb did not have any enhancing effect on the mutagenicity of BP, nor did it exhibit any mutagenic activity in itself with or without S9 mix.